Ultrasonic systems are known for detecting or imaging the internal structures of liquid, solid, and semi-solid materials. In operation, such apparatus typically include a handheld probe that generates a beam, of acoustic signals. The beam is transmitted into the material of interest and is reflected by various gradients or other physical features of the material. The beam may be focussed at various depths within the material and may also be scanned vertically and horizontally so that the reflected acoustic signals may be used to provide three-dimensional image data about various aspects of the material.
In a phased array ultrasound imaging system, the probe includes a transducer array of many transducer elements. Multiple-element transducer arrays consist of a plurality of individual piezoelectric elements, each of which typically features a separate electrical connection to each of paired electrodes. The system includes a multiple channel transmitter and a multiple channel receiver connected through a transmit/receive switch to the transducer. Each transmitter channel causes a selected transducer array element to transmit an ultrasound pulse into an object being imaged. The transmitted ultrasound energy is steered along a transmit scan line and is focused by applying appropriate delays to the pulses transmitted from each transducer array element, so that the transmitted energy adds constructively a desired focal point to form a transmit beam. A part of the transmitted ultrasound energy is reflected back to the transducer array by various structures that are in the path of the transmitted ultrasound energy.
The reflected ultrasound energy from an object or structure arrives at the array elements at different times. The received signals are amplified and are delayed in separate receiver channels and then are summed in a receive beam former to form a receive beam. The delay for each channel is selected such that the receive beam is steered at a desired angle and is focused at a desired depth. The delays may be varied so as to focus the beam at progressively increasing depths along a receive scan line as the ultrasound energy is received. Ultrasound energy may be transmitted along multiple transmit scan lines in a desired scan pattern, such as a sector scan, and the received signals are processed to produce an image of the region of interest. In a particular application of ultrasonic systems in the field of medicine, ultrasonic probes are manipulated for examination of the anatomical parts of a patient. For example, the reflected signals may be received, analyzed, and processed to produce an image display that is representative of the structure of an internal organ, such as the heart.
Modern ultrasonic diagnostic systems have been developed to provide advanced features, such as electronic beam steering and electronic focussing, by using complex electronics for effecting beam forming channels to control the amplitude and phasing of, for example, a one-dimensional (linear array) or two-dimensional (matrixed array) arrangement of transducer elements. The emission of an individual acoustic signal channel in a typical array will require that a transducer element be coupled with a signal provided on a respective beam forming channel. Therefore, in most applications, a large number acoustic signal channels is desirable to provide high resolution acoustic imaging.
Accordingly, a modern diagnostic ultrasound system includes a rather bulky probe having at least one transducer array that features a large number of separate transducer elements, a cable for handling a large number of signals, an electronics unit for supporting the large number of beam forming channels necessary to provide high resolution acoustic imaging. A remotely-located display unit is used for generating the high resolution acoustic image.
Accordingly, one conventional approach to improving the modern diagnostic imaging system is to connect a large number of signal cables to a transducer element array fixed in a compact housing. The probe typically includes a sensor head containing one or more ultrasonic transducer element arrays whereby the transducer elements are electrically connected to an intermediate circuit housed in the sensor head by a short flexible circuit or a connector. The signal cables are provided in a multiconductor cable that is electrically connected to the intermediate circuit, which transmits electrical signals between the transducer array and a signal processing and display apparatus that is connected to the distal end of the cable.
Another approach attempts to miniaturize and integrate some or all of the components of a diagnostic imaging system so as to integrate those components in a portable, handheld unit. That is, such an approach intends to integrate the transducer, cabling, beam former, image processing electronics, display, power source, etc. in a single package. See, for example: U.S. Pat. No. 3,964,296, entitled "Integrated Ultrasonic Scanning Apparatus", and issued to Matzuk; U.S. Pat. No. 4,246,792, entitled "Self-contained Ultrasonic Scanner", and issued to Matzuk; U.S. Pat. No. 5,295,485, entitled "Ultrasonic Diagnostic System", and issued to Shinomura et al.; U.S. Pat. No. 5,617,864, entitled "Method and Apparatus for Positioning an Ultrasonic Transducer and a Display Screen", and issued to Stouffer et al.; U.S. Pat. No. 5,722,412, entitled "Handheld Ultrasonic Diagnostic Instrument", and issued to Pflugrath et al., and U.S. Pat. No. 5,738,099, entitled "Portable Ultrasonic Diagnostic Apparatus", and issued to Chang. This approach adds that is said to result in is a portable unit that is described as "hand-held". However, an examination of the literature shows that such "hand-held" units would appear to be, in practice, difficult to manipulate by less than two hands without assistance. For example, U.S. Pat. No. 3,964,296 describe the use of a support arm mechanism; U.S. Pat. Nos. 5,617,864 and 5,738,099 include a pistol grip or a counter balance device to alleviate the user fatigue associated with manipulation of the apparatus.
Furthermore, some of the foregoing approaches, in an attempt to integrate all of the functions of the diagnostic imaging system into a single portable unit, result in a unit that is likely to be more complex and expensive than is necessary or desirable for some applications. See, for example, U.S. Pat. Nos. 4,246,792 and 5,722,412.
Robustness and reliability are also a concern. A handheld unit can be subject to impact shock, temperature extremes, and other undesirable physical and environmental conditions that ordinarily would not be experienced by those components if they were located in a rack-mounted unit. Accordingly, an attempt to integrate all of the functions of a diagnostic imaging system into a single handheld unit forces the designer to resort to difficult and costly techniques to assure that all of the integrated components meet a diversity of opposing constraints, such as of low weight and mass, high reliability, low-cost, and ease of manipulation.
Hence, there remains a need for an ultrasonic diagnostic imaging system having a probe assembly that incorporates a display and transducer within a single unit, so that the operator can easily view a displayed image while positioning the transducer, wherein the probe assembly is reliable in operation and is small, durable, simple, and inexpensive to construct. There is a further need for such a probe assembly that is integrated in a lightweight package that is susceptible of being manipulated by the fingers of one hand, preferably by grasping the unit between the thumb and forefinger, in order to be easily manipulated by one hand without fatigue. Such a probe assembly would allow the operator to devote one hand to the task of effectively positioning the probe assembly for diagnostic utility, thus freeing the other hand for, e.g., palpitation of the tissue that is being examined, or for operating the controls of the imaging system, or for other tasks. Additionally, such a probe assembly would be especially useful if configured for operation in a confined space, such as in a small body cavity.